In general, semiconductor devices may be manufactured using a plurality of unit processes, such as a thin-film deposition process, a photolithography process, an etching process, an ion implantation process, and a cleaning process. The thin-film deposition process and the etching process are usually performed using a plasma step, in which positive charges are produced from a source gas. However, when the charged source gas is supplied into a chamber provided with a substrate, the charged source gas may lead to contamination of an inner surface and parts of the chamber. Accordingly, a preventive maintenance (PM) step is periodically performed to manage the parts.